Dead simple count down or count up timer for node and in browser using clientmodules or browserify.

For a standalone version that bundles required modules just use time-counter.bundled.js.

This isn't meant to be scientifically amazingly perfect. Because we're just looping and comparing with a start time at a set interval. This approach is a bit flawed because it's impacted by the event loop, etc. But it's good enough for the vast majority of regular web app uses.